Question: I resized an actor and need to keep her that size. Is there a way to reestablish relationships between that actor and other objects without building the relationships from scratch?

Yes. This method can save you a lot of time compared to individual posing objects and saving each relationship from scratch, but it still takes a bit of effort.

1. Place the resized actor on the set.
2. Drag a normal-sized actor of the same general type (male, female, teenage male, teenage female) out of the Object Library and place it on the set.
3. Select the normal actor and the object you want your resized actor to have a relationship with, then right-click and choose the desired relationship.
4. If the resized actor and the object get glued together when the relationship is applied, unglue them.
5. Select the resized actor and the normal actor only. 
6. Click the Objects Menu then Swap Object Positions. The resized actor "jumps" into the position and pose of the regular actor, and vice-versa.
7. Delete the normal actor.
8. Because the resized actor is, well, resized, his or her pose will most likely need some adjusting to make it interact precisely with the other object. Perform any necessary adjustments (Free Position Mode is designed specifically for times like this).
9. If you intend to use your resized actor in this relationship in future, select both the actor and the actor/object with whom they are in a relationship, then right-click and choose "Store New Relationship."